Conventional waste water treatment systems conventionally include, amongst other components, a clarifier or a separator for removing solids from the waste water and an aeration vessel wherein components of the waste water are oxidized. Because a typical installation employs separators and aeration vessels which are separate from each other, they may be more costly from the capital standpoint in that the excavation costs, the costs of forming the vessel, usually out of concrete, erection costs including painting, plumbing and electrical installations are increased over what would be required if but a single vessel were to be made. Operational expenses are likewise increased in that some means must be provided for returning solids from the bottom of the separator back to the aeration tank which might be costly to operate.
To eliminate these problems, in recent years there have been proposals of oxidation vessels provided with internal separators or clarifying devices. One such construction is illustrated in U.S. Pat. No. 4,303,516 issued Dec. 1, 1981 to Stensel et al. Another construction is shown, for example in U.S. Pat. No. 4,383,922 issued May 17, 1983 to Beard. Other similar proposals wherein clarifiers are included in an aeration basin includes the so-called BMTS intrachannel clarifier and a similar design offered by Aero-Mod Inc. of Manhatten, Kan.
While such proposals have eliminated or reduced the above enumerated cost factors associated with systems employing separate clarifiers or separators and aeration vessels, they are not without drawbacks of their own. For example, the clarifier constructions act as a restriction in the channel of the aeration vessel. That is, they act as a transverse baffle. This in turn blocks movement of scum or floating material requiring the presence of some means for removing the scum and the floating material from the sides of the clarifier.
Moreover, the restrictive nature of such systems frequently interferes with the velocity of the waste water moving in the aeration vessel such that velocity gradients may occur. Where a low velocity area is generated, undesirable sludge deposition is likely to occur.
When steps are taken to eliminate the velocity problem, frequently the depth of the vessel in the vicinity of the clarifier will be made much greater. This in turn increases the construction costs and has potential problem posed by the existence of significant ground water or, in the alternative, may require extensive excavation into underlying bedrock.
In others, the design of the clarifier may be such as to allow so-called "short circuiting" meaning that the waste water does not uniformly flow through the entire volume of the separator but takes a path of lesser size. This of course means that the velocity of the waste water in the reduced path is increased over the design velocity which in turn may interfere with the settling of solids in the waste water.
In order to overcome these difficulties, in the commonly owned application of Kersten, Ser. No. 527,015, filed Aug. 29, 1983, now U.S. Pat. No. 4,487,692, and entitled "Sidewall Mounted Separator for Removing Solids and Waste Water" there is proposed a clarifier construction which avoids velocity gradients and which may be easily disposed in existing aeration vessels and/or does not require unusual excavation when installed as part of a newly constructed aeration vessel. The present invention constitutes a further improvement employing the principles of the Kersten separator.